1. Field of the Invention
This invention relates to a medical instrument. More particularly, this invention relates to a medical instrument possessed of a highly reliable connecting part which can be firmly joined.
2. Description of the Prior Art
Various medical instruments such as injection syringes (consisting of a barrel fitted with a plunger and a hollow needle), catheters of varying types, and artificial organs which are in popular use are possessed of a female connector member incorporating a female taper portion and a male connector member incorporating a male taper portion capable of being fitted into the female taper portion.
FIG. 1 illustrates a typical connecting portion which comprises a female connector member 1 incorporating a female taper portion 1a and having a screw thread 1b formed monolithically on the outer periphery thereof and a male connector member 2 incorporating a male taper portion 2a and having a ring member 2c monolithically formed on the outer side thereof and a screw thread 2b formed monolithically on the inner side thereof, so that the female connector member 1 and the male connector member 2 can be firmly and safely joined by fitting the male taper portion 2a into the female taper portion 1a and helically fitting the screw thread 1b into the screw thread 2b. Since the female connector member 1 and the male connector member 2 illustrated in FIG. 1 have their screw threads 1b and 2b formed monolithically thereon, however, the angle and position of connection in the relative rotational directions around their axes cannot be selected at will at the time the connector members are joined to each other, and they are sometimes loosened.
FIG. 2 illustrates a medical instrument which comprises a medical instrument member Y and a medical instrument member X, the member Y having a female connector member 3 incorporating a female taper portion 3a and having a stationary screw thread 3b formed on the outer periphery thereof and the member X having a male connector member 4 incorporating a male taper portion 4a and having rotatably mounted on the outer periphery thereof a rotary ring 5 incorporating a rotary screw thread 5a so that the rotary ring 5 is prevented from moving in the axial direction toward the leading end of the medical instrument by the union between the rotary ring 5 and an engaging portion 4c of the male connector member 4. In this arrangement, the female connector member 3 and the male connector member 4 are enabled to join each other by fitting the male taper portion 4a into the female taper portion 3a and, at the same time, helically fitting the rotary screw thread 5a into the stationary screw thread 3b. In the case of the female connector member 3 and the male connector member 4 illustrated in FIG. 2, the angle and position of connection in their relative rotational directions around their axes can be selected at will because the rotary ring 5 is rotatably mounted relative to the male connector member 4. Owing to this merit, the union of the connector members 3 and 4 can be advantageously utilized in a medical instrument such as a three-way faucet for which directionality counts much.
In the example illustrated in FIG. 2, the union of the member X and the member Y of the medical instrument is accomplished by bringing the male taper portion 4a and the female taper portion 3a into mutual contact. The helical engagement between the rotary screw thread 5a of the rotary ring 5 and the stationary screw thread 3b, therefore, is adapted to avoid interfering with the coming into contact of the aforementioned taper portions 4a and 3a. As the result, the surface area of contact between the stationary screw thread 3b of the female connector member 3 and a rotary screw thread 5a of the rotary ring 5 and the surface area of contact between the engaging portion 4c of the male connector member 4 and the rotary ring 5 are both small and the rotary ring 5 is liable to produce idle rotation relative to the female connector member 3 and the male connector member 4. When the engagement between the female taper portion 3a and the male taper portion 4a becomes loose, the pressure of the fluid flowing inside the member Y of the medical instrument exerts a force tending to urge the member X of the medical instrument outwardly. It is for the purpose of preventing the otherwise possible separation of the member X in this case that the present medical instrument is furnished with the rotary ring 5 at all. Since the rotary ring 5 has a small surface area of contact and is liable to generate idle rotation as described above, it is eventually rotated in the direction of separation by the aforementioned outwardly urging force. It is, therefore, difficult for the helical engagement between the stationary screw thread 3b of the female connector member 3 and the rotary screw thread 5a of the rotary ring 5 to ensure preclusion of the possibility of separation between the female taper portion 3a of the female connector member 3 and the male taper portion 4a of the male connector member 4.
In illustrated the example illustrated FIG. 2, there may be conceived an idea of adapting a shaft 6 of the male connector member 4 and a hole 7 of the rotary ring 5 so that they have mutually ground surfaces for safer union. In this case, however, the male connector member 4 detracts from smoothness of rotation relative to the rotary ring 5 and the male connector member 4 experiences difficulty in securing free directionality. Thus, this idea proves unsatisfactory. Alternately, there may be conceived an idea of adapting the stationary screw thread 3b of the female connector member 3 and the rotary screw thread 5a of the rotary ring 5 so as to have mutually ground thread surfaces for safer union. In this case, the stationary screw thread 3b of the female connector member 3 and the rotary screw thread 5a of the rotary ring which have their thread surfaces ground against each other are required to be used as pair at all times. Incidentally, the female connector member 3 and the male connector member 4 are intended to be joined in a freely selected combination. Thus, there are times when the female connector member 3 and the male connector member 4 randomly selected cannot be solidly and safely joined to each other because their screw threads fail to form the pair mentioned above.
An object of this invention, therefore, is to provide a novel medical instrument.
Another object of this invention is to provide a medical instrument to connect both of the medical instrument members X shown in the prior art which enables the female connector member and the male connector member to be firmly and safely joined, and a medical instrument fitting the medical instrument members.